You plan to migrate from a third-party IMAP email system to an Office 365 tenant. You must ensure that the tenant passes the health, readiness, and connectivity steps. The solution must also provide step-by-step assistance to migrate email account. You need to plan the migration. What should you do?

Use the Office 365 Setup wizard to perform an IMAP migration.
The advance setup wizard can run automated checks to discover how your current environment is set up and then, based on what is found, recommend a path to
Office 365. If you tell Office 365 Setup wizard that your source email system uses IMAP, and you have fewer than 151 mailboxes, it recommends that you use the
Office 365 Setup wizard to copy your users email to Office 365 by using IMAP migration.
References:https://support.office.com/en-us/article/Use-the-Office-365-Setup-wizard-to-perform-an-IMAP-migration-d0800530-22fa-4ec5-9a29-efe900f2e3d0